Strong Electroweak Symmetry Breaking

TL;DR

This paper discusses strong electroweak symmetry breaking models, highlighting their theoretical appeal, challenges faced by minimal technicolor models, and proposes a generic search strategy based on features of walking technicolor for LHC experiments.

Contribution

It introduces the Technicolor Straw Man, a model-independent search strategy focusing on light, narrow technivector mesons as a signature of strong electroweak symmetry breaking.

Findings

Minimal technicolor models are ruled out by experimental constraints.

Walking technicolor predicts light, narrow technivector mesons.

The Straw Man strategy guides experimental searches for strong EW breaking signals.

Abstract

Models of spontaneous breaking of electroweak symmetry by a strong interaction do not have fine tuning/hierarchy problem. They are conceptually elegant and use the only mechanism of spontaneous breaking of a gauge symmetry that is known to occur in nature. The simplest model, minimal technicolor with extended technicolor interactions, is appealing because one can calculate by scaling up from QCD. But it is ruled out on many counts: inappropriately low quark and lepton masses (or excessive FCNC), bad electroweak data fits, light scalar and vector states, etc. However, nature may not choose the minimal model and then we are stuck: except possibly through lattice simulations, we are unable to compute and test the models. In the LHC era it therefore makes sense to abandon specific models (of strong EW breaking) and concentrate on generic features that may indicate discovery. The Technicolor Straw Man is not a model but a parametrized search strategy inspired by a remarkable generic feature of walking technicolor, that technivector mesons are light, narrow and decay readily into electroweak vector mesons and photons. While walking technicolor is popular among practitioners, alternatives exist and the Straw Man may not lead to their discovery.